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/** @file Implementation of the Terragen importer class */


#ifndef ASSIMP_BUILD_NO_TERRAGEN_IMPORTER

#include "TerragenLoader.h"
#include "StreamReader.h"
#include <assimp/Importer.hpp>
#include <assimp/IOSystem.hpp>
#include <assimp/scene.h>
#include <assimp/DefaultLogger.hpp>
#include <assimp/importerdesc.h>

using namespace Assimp;

static const aiImporterDesc desc = {
    "Terragen Heightmap Importer",
    "",
    "",
    "http://www.planetside.co.uk/",
    aiImporterFlags_SupportBinaryFlavour,
    0,
    0,
    0,
    0,
    "ter"
};

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
TerragenImporter::TerragenImporter()
: configComputeUVs (false)
{}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
TerragenImporter::~TerragenImporter()
{}

// ------------------------------------------------------------------------------------------------
// Returns whether the class can handle the format of the given file.
bool TerragenImporter::CanRead( const std::string& pFile, IOSystem* pIOHandler, bool checkSig) const
{
    // check file extension
    std::string extension = GetExtension(pFile);

    if( extension == "ter")
        return true;

    if(  !extension.length() || checkSig)   {
        /*  If CanRead() is called in order to check whether we
         *  support a specific file extension in general pIOHandler
         *  might be NULL and it's our duty to return true here.
         */
        if (!pIOHandler)return true;
        const char* tokens[] = {"terragen"};
        return SearchFileHeaderForToken(pIOHandler,pFile,tokens,1);
    }
    return false;
}

// ------------------------------------------------------------------------------------------------
// Build a string of all file extensions supported
const aiImporterDesc* TerragenImporter::GetInfo () const
{
    return &desc;
}

// ------------------------------------------------------------------------------------------------
// Setup import properties
void TerragenImporter::SetupProperties(const Importer* pImp)
{
    // AI_CONFIG_IMPORT_TER_MAKE_UVS
    configComputeUVs = ( 0 != pImp->GetPropertyInteger(AI_CONFIG_IMPORT_TER_MAKE_UVS,0) );
}

// ------------------------------------------------------------------------------------------------
// Imports the given file into the given scene structure.
void TerragenImporter::InternReadFile( const std::string& pFile,
    aiScene* pScene, IOSystem* pIOHandler)
{
    IOStream* file = pIOHandler->Open( pFile, "rb");

    // Check whether we can read from the file
    if( file == NULL)
        throw DeadlyImportError( "Failed to open TERRAGEN TERRAIN file " + pFile + ".");

    // Construct a stream reader to read all data in the correct endianness
    StreamReaderLE reader(file);
    if(reader.GetRemainingSize() < 16)
        throw DeadlyImportError( "TER: file is too small" );

    // Check for the existence of the two magic strings 'TERRAGEN' and 'TERRAIN '
    if (::strncmp((const char*)reader.GetPtr(),AI_TERR_BASE_STRING,8))
        throw DeadlyImportError( "TER: Magic string \'TERRAGEN\' not found" );

    if (::strncmp((const char*)reader.GetPtr()+8,AI_TERR_TERRAIN_STRING,8))
        throw DeadlyImportError( "TER: Magic string \'TERRAIN\' not found" );

    unsigned int x = 0,y = 0,mode = 0;

    aiNode* root = pScene->mRootNode = new aiNode();
    root->mName.Set("<TERRAGEN.TERRAIN>");

    // Default scaling is 30
    root->mTransformation.a1 = root->mTransformation.b2 = root->mTransformation.c3 = 30.f;

    // Now read all chunks until we're finished or an EOF marker is encountered
    reader.IncPtr(16);
    while (reader.GetRemainingSize() >= 4)
    {
        const char* head = (const char*)reader.GetPtr();
        reader.IncPtr(4);

        // EOF, break in every case
        if (!::strncmp(head,AI_TERR_EOF_STRING,4))
            break;

        // Number of x-data points
        if (!::strncmp(head,AI_TERR_CHUNK_XPTS,4))
        {
            x = (uint16_t)reader.GetI2();
        }
        // Number of y-data points
        else if (!::strncmp(head,AI_TERR_CHUNK_YPTS,4))
        {
            y = (uint16_t)reader.GetI2();
        }
        // Squared terrains width-1.
        else if (!::strncmp(head,AI_TERR_CHUNK_SIZE,4))
        {
            x = y = (uint16_t)reader.GetI2()+1;
        }
        // terrain scaling
        else if (!::strncmp(head,AI_TERR_CHUNK_SCAL,4))
        {
            root->mTransformation.a1 = reader.GetF4();
            root->mTransformation.b2 = reader.GetF4();
            root->mTransformation.c3 = reader.GetF4();
        }
        // mapping == 1: earth radius
        else if (!::strncmp(head,AI_TERR_CHUNK_CRAD,4))
        {
            reader.GetF4();
        }
        // mapping mode
        else if (!::strncmp(head,AI_TERR_CHUNK_CRVM,4))
        {
            mode = reader.GetI1();
            if (0 != mode)
                DefaultLogger::get()->error("TER: Unsupported mapping mode, a flat terrain is returned");
        }
        // actual terrain data
        else if (!::strncmp(head,AI_TERR_CHUNK_ALTW,4))
        {
            float hscale  = (float)reader.GetI2()  / 65536;
            float bheight = (float)reader.GetI2();

            if (!hscale)hscale = 1;

            // Ensure we have enough data
            if (reader.GetRemainingSize() < x*y*2)
                throw DeadlyImportError("TER: ALTW chunk is too small");

            if (x <= 1 || y <= 1)
                throw DeadlyImportError("TER: Invalid terrain size");

            // Allocate the output mesh
            pScene->mMeshes = new aiMesh*[pScene->mNumMeshes = 1];
            aiMesh* m = pScene->mMeshes[0] = new aiMesh();

            // We return quads
            aiFace* f = m->mFaces = new aiFace[m->mNumFaces = (x-1)*(y-1)];
            aiVector3D* pv = m->mVertices = new aiVector3D[m->mNumVertices = m->mNumFaces*4];

            aiVector3D *uv( NULL );
            float step_y( 0.0f ), step_x( 0.0f );
            if (configComputeUVs) {
                uv = m->mTextureCoords[0] = new aiVector3D[m->mNumVertices];
                step_y = 1.f/y;
                step_x = 1.f/x;
            }
            const int16_t* data = (const int16_t*)reader.GetPtr();

            for (unsigned int yy = 0, t = 0; yy < y-1;++yy) {
                for (unsigned int xx = 0; xx < x-1;++xx,++f)    {

                    // make verts
                    const float fy = (float)yy, fx = (float)xx;
                    unsigned tmp,tmp2;
                    *pv++ = aiVector3D(fx,fy,    (float)data[(tmp2=x*yy)    + xx] * hscale + bheight);
                    *pv++ = aiVector3D(fx,fy+1,  (float)data[(tmp=x*(yy+1)) + xx] * hscale + bheight);
                    *pv++ = aiVector3D(fx+1,fy+1,(float)data[tmp  + xx+1]         * hscale + bheight);
                    *pv++ = aiVector3D(fx+1,fy,  (float)data[tmp2 + xx+1]         * hscale + bheight);

                    // also make texture coordinates, if necessary
                    if (configComputeUVs) {
                        *uv++ = aiVector3D( step_x*xx,     step_y*yy,     0.f );
                        *uv++ = aiVector3D( step_x*xx,     step_y*(yy+1), 0.f );
                        *uv++ = aiVector3D( step_x*(xx+1), step_y*(yy+1), 0.f );
                        *uv++ = aiVector3D( step_x*(xx+1), step_y*yy,     0.f );
                    }

                    // make indices
                    f->mIndices = new unsigned int[f->mNumIndices = 4];
                    for (unsigned int i = 0; i < 4;++i)
                        f->mIndices[i] = t++;
                }
            }

            // Add the mesh to the root node
            root->mMeshes = new unsigned int[root->mNumMeshes = 1];
            root->mMeshes[0] = 0;
        }

        // Get to the next chunk (4 byte aligned)
        unsigned dtt;
        if ((dtt = reader.GetCurrentPos() & 0x3))
            reader.IncPtr(4-dtt);
    }

    // Check whether we have a mesh now
    if (pScene->mNumMeshes != 1)
        throw DeadlyImportError("TER: Unable to load terrain");

    // Set the AI_SCENE_FLAGS_TERRAIN bit
    pScene->mFlags |= AI_SCENE_FLAGS_TERRAIN;
}

#endif // !! ASSIMP_BUILD_NO_TERRAGEN_IMPORTER